Kensington Orbit Trackball

Orbit trackball only has two buttons. Enable middle mouse emulation (press both buttons to middle click).

Listing 1: /etc/X11/xorg.conf.d/50-kensington_orbit_wireless.conf

Section "InputClass"
    Identifier   "Kengington Orbit"
    MatchProduct "MOSART Semi. Orbit Wireless Mobile Trackball"
    Option       "Emulate3Buttons" "true"
EndSection